The escalating threat of multidrug-resistant pathogens necessitates innovative approaches to combat infectious diseases. In this study, we examined peptides R23F^S*, V31K^S*, and R44K^S*, which were engineered to include an amyloidogenic fragment sourced from the S1 protein of S. aureus, along with one or two cell-penetrating peptide (CPP) components. We assessed the antimicrobial efficacy of these peptides in a liquid medium against various strains of both Gram-positive bacteria, including S. aureus (209P and 129B strains), MRSA (SA 180 and ATCC 43300 strains), and B. cereus (strain IP 5832), and Gram-negative bacteria such as P. aeruginosa (ATCC 28753 and 2943 strains) and E. coli (MG1655 and K12 strains). Peptides R23F^S*, V31K^S*, and R44K^S* exhibited antimicrobial activity comparable to gentamicin and meropenem against all tested bacteria at concentrations ranging from 24 to 48 μM. The peptides showed a stronger antimicrobial effect against B. cereus. Notably, peptide R44K^S* displayed high efficacy compared to peptides R23F^S* and V31K^S*, particularly evident at lower concentrations, resulting in significant inhibition of bacterial growth. Furthermore, modified peptides V31K^S* and R44K^S* demonstrated enhanced inhibitory effects on bacterial growth across different strains compared to their unmodified counterparts V31K^S and R44K^S. These results highlight the potential of integrating cell-penetrating peptides, amyloidogenic fragments, and amino acid residue modifications to advance the innovation in the field of antimicrobial peptides, thereby increasing their effectiveness against a broad spectrum of pathogens.

The development of novel antimicrobial peptides (AMPs) with broad-spectrum activity represents a promising strategy to overcome multidrug resistance in pathogenic bacteria. In this study, we investigated the antimicrobial activity of three designed peptides—R44K^S*, V31K^S*, and R23F^S*—engineered to incorporate an amyloidogenic fragment from the S1 protein of Staphylococcus aureus and one or two cell-penetrating peptide (CPP) fragments to enhance cellular uptake. The antimicrobial efficacy of these peptides and their combinations was assessed against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and Bacillus cereus. The results demonstrated that all three peptides exhibited significant antibacterial activity in a concentration-dependent manner, with R44K^S* being the most potent. Peptide combinations, particularly V31K^S*/R23F^S* and R44K^S*/V31K^S*, showed enhanced inhibitory effects and reduced minimum inhibitory concentrations (MICs), suggesting synergistic or additive interactions. Fractional inhibitory concentration index (FICI) analysis confirmed that most combinations exhibited synergy or additive effects. These findings highlight the potential of CPP-modified peptides as antimicrobial agents and underscore the importance of optimizing peptide combinations for therapeutic applications.

Nucleated erythroid cells (NECs) are emerging as important immunoregulators at the feto–maternal interface, yet their chemokine profiles and functional dynamics across pregnancy remain poorly understood. Using a murine allogeneic pregnancy model (CBA × C57Bl/6), we isolated placental and splenic TER-119⁺ NECs at mid- (E12.5) and late (E19.5) gestation. Chemokine production (13-plex), chemokine receptor expression (qPCR), immunosuppressive molecules (PD-L1, TGF-β, and ROS), T-cell proliferation (CFSE), and immune cell migration (Transwell) were assessed. CD45⁺ placental NECs were the main producers of PD-L1, TGF-β, and ROS, with maximal expression at E19.5, suggesting their potential contribution to the immunosuppressive functions observed in the total TER-119⁺ population. Chemokine production showed a striking shift in CCL17 and CXCL9 from the spleen to the placenta as pregnancy advanced (E12.5 → E19.5). Splenic NECs displayed dominant expressions of CCR3 and CXCR4. Unexpectedly, CCL2 and CCL4 blockade enhanced immune cell migration toward placental NECs at E19.5. Placental nucleated erythroid cells potently suppressed T-cell proliferation at E12.5, and this suppressive capacity remained stable until full term. Placental NECs undergo dynamic chemokine reprogramming while maintaining stable T-cell suppression. The paradoxical enhancement of migration after CCL2/CCL4 blockade suggests a complex chemokine network warranting further investigation. These findings provide new insights into the immunobiology of pregnancy and may have implications for understanding pregnancy complications.